Shallow-draft boat

ABSTRACT

A shallow-draft boat that is operated by omni-directional thruster means lying below the flat hull, which is stabilized and protected by one or more skegs. The boat has a high beam-tolength ratio, a low depth-to-length ratio, and a low depth-tobeam ratio. Its hull is double-ended and symmetric along both the longitudinal axis and the transverse axis, and the hull has a fully developable surface enabling construction from flat plates without compound curving. One embodiment, especially useful as a harbor tugboat, has a high, centrally located deckhouse with an entry well above deck level; this deckhouse is water-tight at the deck, and it may be hinged to swing about 90* for open access to the hold; the engines lie below this deckhouse and project up into its lower part. Buoyancy compartments are preferably provided at each end, and in some forms of the invention at least one end has adjustable and retractable pusher knees. Other modified forms are simpler and have different special adaptations.

United States Patent 1 1 Seymour et al.

l l J,Iuv,uur

[ 1 Aug. 7, 1973 I SHALLOW-DRAFT BOAT I 22 Filed: June 23,1971

21 Appl.No.: 155,764

[52] US. Cl. 114/65 R, 114/235 R [51] Int. Cl B63b 3/00 [58] Field of Search 114/56, 53, 60, 63, 114/65, 66, 70, 71,123, 218, 235; 9/6; 115/28, 35

[56] References Cited UNITED STATES PATENTS 1,397,405 11/1921 Dedik 114/123 2,039,399 5/1936 Englis 114/70 2,710,587 6/1955 Kutchar 114/57 2,794,410 6/1957 Oliver et al. 115/35 2,902,966 9/1959 Baer 114/235 R 3,362,372 1/1968 Peterson 114/235 R 3,546,888 12/1970 Kolb et al.-, 114/235 R FOREIGN PATENTS OR APPLICATIONS 723,378 2/1955 Great Britain 114/71 Primary ExaminerMilton Buchler Assistant Examiner-Jesus D. Sotelo Attorney0wen, Wickersham & Erickson [57] ABSTRACT A shallow-draft boat that is operated by omnidirectional thruster means lying below the flat hull, which is stabilized and protected by one or more skegs. The boat has a high beam-to-length ratio, a low depthto-length ratio, and a low depth-to-beam ratio. Its hull is double-ended and symmetric along both the longitudinal axis and the transverse axis, and the hull has a fully developable surface enabling construction from flat plates without compound curving. One embodiment, especially useful as a harbor tugboat, has a high, centrally located deckhouse with an entry well above deck level; this deckhouse is water-tight at the deck, and it may be hinged to swing about 90for open access to the hold; the engines lie below this deckhouse and project up into its lower part. Buoyancy compartments are preferably provided at each end, and in some forms of the invention at least one end has adjustable and retractable pusher knees. Other modified forms are simpler and have different special adaptations.

1 20 Claims, 16 Drawing Figures PATENTEDAUG 7197a I 3,750,607

sum 1 0F 5 I NVENTORS DAVID J. SEYMOUR DAVID MARTIN ATTORNEYS PAIENIE AUG H975 INVENTORS DAVID J. SEYMOUR BY DAVID MARTIN FlG 1O FlG 11 ATTORNEYS PATENTEU AUG H973 3750,60?

SHEEI 5 0F 5 FlG ..14

FlG 15 FlG 16 INVENTORS DAVID J. SEYMOUR DAVID MARTIN a ga- ATTQRNEYS SHALLOW-DRAIFT soar BACKGROUND OF THE INVENTION This invention relates to an improved shallow-draft boat.

The invention has many uses. It can be used to provide an improved tugboat, or a better work boat, and it can be used for many other types of work where relatively wide shallow boats have particular utility.

An especially important embodiment is a harbor tugboat that provides more efficient services in ship handling, barge towing, fire fighting, salvage, and miscellaneous other operations in harbors, bays and inland waters, and coastal waterways.

While tugboats have been in use for many years, improvements in their design, construction and operation have been gradual and have mostly been confined to details or to separate sub-systems. Thus, although individual components were bettered, they often became relatively ineffective when the improved components were combined with each other, and in fact they tended to limit the maximum overall improvement of the tugboats capability.

For example, tugboats have heretofore universally been designed with large-diameter fixed-directional propellers providing the desired levels of thrust. This approach resulted in relatively deep drafts'for harbor tugboats, often preventing their use in shallow inland waters. Also, the fixed direction of thrust limited the tugboats ability to handling vessels only by pushing or pulling them parallel to the centerline of the tugboat's hull; not only could such tugboats not apply thrust in any direction other than "fore or aft, but also they lacked the necessary transverse stability to resist, without danger of capsizing, heeling from applying such sideway thrust. Also in ship handling and docking of large vessels, where tugboats make fast alongside parallel to the vessels centerline (and this is the normal method in most'United States ports), a rapid application of tugboat thrust normal to the vessels centerline could not be applied without completely reorienting the tugboat together with excessively high torque on the rudder. Such an operation required manhandling of lines by the boats crew and considerable time; in some cases, such an operation became impossible because of insufficient room between the ship and dock, or be- I cause of other vessels or restrictionsin the close vicinity.

Designers of tugboats have traditionally incorporated ship-shape forms for tug hulls, with bow and stem lines having compound curvature of shell plating; Such forms necessitate high construction costs, whereas simple straight-framed sections with fully developable shell plating are much less expensive. in any event, numerous shipyards were developed specifically for efficiently constructing such high-cost traditional tugboats.

Another problem with most tugboats has been that their general hull configuration gave relatively small andconfining deck areas which restricted optimum location of towing winches and mooring devices and restricted efficient action of the crew when handling lines both fore and aft. I

In addition to the fact that propeller thrust of priorart tugboats was unidirectional, the hull configuration of such tugboats was asymmetrical from bow to stern, and this configuration also imposed this unidirectional feature. Therefore, prior-art tugboats have been greatly handicapped and unable to achieve optimum performance in most tugboat operations without releasing and changing hawsers, lines, etc., to re-orient the tugboat so that it could push in the desired position.

While prior-art tugboats have had what has been considered good maneuverability, especially when special rudders, flanking rudders, nozzles, etc., have been installed, there has long been room for great improvement in this feature, too. Part of the trouble is due to the fact that tugboats have often been designed for use limited to one kind of specialized operation, rather than for versatile capability; for example, when a tugboat has been designed for pushing, special pusher knees have been permanently installed, but these knees sometimes interfered with changing from a pushing'to a pulling operation.

Tugboats have had increasing power levels of propulsion machinery installed, partly to meet demands for high thrust levels in handling ships and barges, andpartly to overcome their inefficient propulsive coeffi' cient in transferring engine horsepower into useful thrust, because of their undesirable hydrodynamic-hull forms and their limited propeller characteristics. These inefficiencies have been most undesirable andhave not been solved by the resort to a brute-force type of approach.

Tugboats have also had many problems with capsizing and foundering, due to their low levels of freeboard, low reserve buoyancy and inadequate stability. Their poor resistance to heeling and deck-edge submergence under operating conditions have often resulted in their being in irons, causing them to capsize' and sink.

The pilot house of prior-art tugboats has often afforded poor visibility, due to its low elevation above water, so that some tugboats have had double pilot houses, a lower one for normal operations and a higher.

one end of the tug or near one end, so that visibility has.

been more restricted when going in one direction than when going in another.

BRIEF SUMMARY OF THE INVENTION The boat of the invention is characterized by having a novel shallow-draft hull that is symmetrical, both longitudinally and transversely, and by being operated by omnidirectional power-thruster means. The boat may have a single power thruster or, in many instances, it is preferable to have two controllable power thrusters, sometimes with both located in the rear, sometimes with one located in front of the other. More than two thrusters may be used in any number of separate locations.

Although some prior-art boats have been operated by a single thruster, their hull configuration, structure, and propulsion system have not beencapable of utilizing their maximum potential. The hull'of this invention has a novel configuration and a number of structural features that cooperate with its thruster system to impart quite a different and improved operation from boats previously in use. It has a wide beam in relation to its length, i.e., a high beam-to-length ratio. It also has a low depth-to-length ratio. It is double-ended. The hull form is depicted by straightdine frames, so that the structure is greatly simplified and a fully developable surface can be generated to form the hull shell. This enables straight flat steel plates to be placed on the hull, so that no compound curving is necessary. The flat plates thus lie on straight frames, and this structure eliminates the cost of special forming of plates and shapes by heating, forging, braking, rolling or constructing special jigs, molds, etc.

The hull has a flat bottom with no keel, but one or more skegs is used; there may be one skeg at each end or two skegs at one end. The skegs provide both directional stability and protection of the thruster units.

The boat of this invention has exceptionally good di' rectional stability and exceptionally remarkable high maneuverability. Even should there be failure of one thruster, the other thruster can still maneuver the boat with a high level of maneuverability, although its thrust is only one-half of the two-thruster value. The tugboat form of this invention has a very fast response system. It can stop faster and change direction faster than tugboats heretofore in use. When used for ship handling, it has a high degree of versatility in the direction of thrust application and can either push or pull, either parallel or sideways, where it is attached alongside a ship parallel to the ship. For barge handling, it can be used either for pull towing or push towing and can also be used for alongside towing.

The tugboat of this invention preferably has a high central tower which combines the tugboat functions for conning, navigating, firefighting, supporting smokestacks, navigational lights and equipment, housing of crew accommodations, stowage of salvage equipment and vessel's stores. This high central tower is also used on forms of the invention other than tugboats for the same general purposes, depending upon the size and purpose of the boat.

The present invention provides a combination of a shallow and wide hull with omni-directional thrusters and with skeg means, either incorporated in a unit with the thrusters or separately therefrom. This combination is very effective for tugboats and has many other uses. It can be used for a work boat having a much simpler construction than a harbor tug, and such a work boat may have a central symmetrical tower that is less complex than is desirable on a harbor tug. The combbination can also be used as a tender for vessels designed to carry small barges pre-loaded with cargo, again with a central tower of simpler structure. Such tending operations require tugboats that are much more maneuverable than are conventional tugboats. Various modifications are possible for meeting specific types of problems.

The tugboat form of the invention is also characterized by having large, clear deck spaces, and its central deck house preferably has no openings in it at the deck level, thus being watertight. This structure provides sufficient reserve buoyancy which, together with the vessels high inherent transverse stability, makes it impossible for the boat to capsize by listing or heeling. Moreover, to give easy access to the interior of the hold below deck, the entire deck house can be made to swing on hinges to open up the entire cavity.

Buoyancy compartments above the deck at each end of the tugboat are designed to serve as additional reserve buoyancy, which, together with the vessels high inherent stability, resists trimming by the bow or stem sufficiently to sink the boat; these buoyancy compartments also improve the transverse stability. The propulsion engines protrude through the deck of the shallow hull into the deckhouse in the center of the ship in such a way that the watertight deckhouse protects the engines from any water shipped on deck, as well as providing reserve buoyancy for the tugboat.

A preferred tugboat of the invention is provided with hinged adjustable pusher knees at the stern, which are moved into one position for pushing and are readily retracted flush into the hull, thus eliminating the interference of the large, unwieldy, cumbersome prior-art pusher knees when they are not being used.

A workboat version of this invention is a much simpler structure and a smaller boat than the tugboat, but it has many of the advantages that have already been described which flow from the use of the shallow, wide hull in combination with thruster means. Here, permanently erected pusher knees may be used and the tower may be much simpler, for it need not open into a hold and need not pivot, but it is centrally located and tall, and has some important advantages. The engines in this instance may be located aft and project above the deck itself, and the buoyancy compartments may be eliminated.

Another form of the invention employs a hull that has fore and aft slots enabling the use of a particular type of combination thruster-and-skeg unit which can be moved angularly through the slots.

Other objects and advantages of the invention will appear from the following description of a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a view in perspective of a harbor tugboat embodying the principles of the invention.

FIGS. 2 is a similar view, showing the deckhouse swung on its hinges to open the machinery compartment in the hold of the vessel.

FIG. 3 is an outboard profile of the tugboat of FIG. ll.

FIG. 4 is a view in end elevation of the same.

FIG. 5 is an enlarged view of an inboard profile of the tugboat of FIG. 1, including the first level of the deckhouse.

FIGS. 6, 7, and 8 comprise a lines plan depicting the full form.

FIG. 6 is a profile view of the lines plan showing the shape of the hull profile superimposed on a grid of horizontal lines or water lines, and vertical lines or stations.

FIG. 7 is a plan view of the lines plan showing the shape of the water lines.

FIG. 8 is a sectional view or body plan of the lines plan showing the shape of each station located on the profile view, FIG. 6.

FIG. 9 is a view in perspective of a modified form of boat embodying the principles of the invention and usable as a tender and for other similar uses requiring considerable maneuverability.

FIG. 10 is an outboard profile view of the boat of FIG. 9, showing the fore and aft location of the thruster skeg units, which are mounted in slots in the hull.

FIG.11 is a deck plan view of the boat of FIGS. 9 and It).

FIG. 12 is a diagrammatic bottom view of a modified form of hull as seen from below, showing the location of a pair of thruster and skeg units.

FIG. 13 is a view similar to FIG. 12, showing another modified form of boat having only one thruster and one skeg adjacent to it.

FIG. 14 is an outboard profile view of another modified form of boat embodying the principles of the invention, intended for use as a work boat.

FIG. 15 is a deck plan view of the boat of FIG. 14.

FIG. 16 is a view in end elevation of the boat of FIG.

DESCRIPTION OF SOME PREFERRED EMBODIMENTS A Harbor Tugboat (FIGS. l-8) FIGS.l-8 show a harbor tugboat 10 which is fully symmetric along both its lengthwise, or longitudinal, axis and its widthwise, or transverse, axis. It has a hull 11 which is symmetric both fore and aft and side to side, and it has a similarly symmetric deck 12 with a centrally located deckhouse 13, all of which have important features.

The hull 111 of this tugboat 10 has a very shallow draft, and the boat 10 employes a pair of omnidirectional thrusters l4 and as the propulsion power. The thrusters 14 and 15 project below the flat bottom of the hull 11, giving them better hydrodynamic performance for developing full thrust in smooth and unobstructed water flow under the hull 11. The typical draft of the hull 11 of a tugboat 10 of this invention is about 6 feet, and it has a ratio typically of about 1:6 between the draft and the beam, whereas most tugboats have draft which double that or more. For example, in this invention, a 6-foot draft with a 36-foot beam gives a draft-to-beam ratio of 1:6, whereas typical tugboats would have about a thirteen-foot draft and a 23-foot beam, giving a draft-to-beam ratio of only 1:1:8.

The beam is also wide in relation to the length of the tugboat 10, thereby giving the tugboat 10 a very high level of transverse stability and enabling it to push sidewise, with full thrust, without capsizing. For example, the tugboat 10 may be thirty-six feet wide and have an overall length of 103 feet and an 85-foot water-line length. The ratio of the beam width to the water-line length in this instance is about 1:24, whereas most tugboats are about 23 feet wide at the beam for an 85-foot water-line length, giving a ratio of about 113.7.

The depth of the hull 11 is shallow in relation to the length of the tugboat 10, and this ratio also imparts a high level of transverse and longitudinal stability. For example, the hull 11 may have a depth of 12 feet and an overall length of 103 feet, giving a depth-to-length ratio of 1.9, whereas most tugs for this length would have a depth-to-length ratio of 1:7 or less.

The freeboard of the hull 11 may be 6 feet, whereas for most tugboats of this length the hull freeboard is about 2 to 3 feet for lengths of 80 to 100 feet. This high freeboard explains why the tugboat 10 of this invention has exceptionally high stability to resist heeling moments from the thrusters l4 and 15 when pushing sideways. In terms of freeboard-to-length ratio, conventional tugboats have such ratios in the order of 1:40 to 1:33, or an average of about 1:36. The present invention provides a freeboard-to-length ratio of about 1:14. As a result, the boat 10 has excellent transverse stability, making the vessel practically unsinkable.

The hull 11 of this invention is double-ended, having a flat wall 16, 17 at both ends and also having a flat wall 18, 19 along each side, flat vertically as well as horizontally and a flat bottom 20; it has flat sloping transition portions 21, 22 comprising a double chine bilge and raking fore and aft and is curved at the corners only. As a result, it has the same hydrodynamic efficiency in both directions for pulling and pushing, and it also has the same efficiency on both sides when going beside a ship, and it can lie flush alongside such a ship because of this flat shape. This hull structure saves greatly in the cost of construction, because one side of the tugboat 10 is a mirror image of the other side, so that parts can be made up and put together as duplicate parts in opposite hands.

The hull 11 of this tugboat has no keel, but it has a pair of skegs 25 and 26. There may be one skeg at each end, or there may be two skegs at one end. In either event, the skegs 2S and 26 provide directional stability when the tugboat 10 is running free at full speed, and they protect the thrusters 14, 15 from engaging the bottom in shallow water. They are, or one of them is, located in close proximity to the thrusters l4, 15 in order to help protect them.

FIGS. 6, 7 and 8 constitute a lines plan depicting the form of the hull 11 and its relationship to the skegs 25, 26 and to the power thrusters 14, 15.

FIG. 6 is a profile view showing a base line at the bottom surface of the skegs 25, 26, and, above that, the 2- foot water-line, 4-foot water-line, 6-foot water-line, 8- foot water-line, 10-foot water-line, 12-foot water-line, the actual load waterline LWL, and, above that, the 14- foot, 16-foot and 18-foot water-lines, and the main deck level. Near the right-hand or bow end of the drawing is shown the bow profile line, which intersects the load water-line LWL at the FP (forward perpendicular) station and at the left end is the stern profile line which intersects similarly at the AP (after perpendicular) station. The distance between F? and AP, known as the length between perpendiculars is divided into ten equal stations, with additional half stations at 1%, 8%, and 9%. There are also stations beyond the FF and AP used to indicate the shape of the hull at the ends of the hull 11. The outboard knuckle and inboard knuckle are shown, as are the buoyancy tank and bulwarks. This view depicts the outboard and inboard knuckles as straight lines, the hull 11 as symmetrical, the thrusters l4 and 15 as located below the water-line and below the lowest level of the hull proper, where they have no interference from the hull 11, and the skegs 25, 26 as located relative to the hulll l to give the desired stability without requiring a keel.

FIG. 7 is a view showing the water-lines in relation to one half of the symmetrical hull 11 as viewed in plan. Thus, a series of lines is shown on the forward end in relation to various water-lines, the main deck line, the inboard knuckle, and others, all appropriately labeled and which depict the shape of the water-line at each of these levels, including the load water-line LWL.

FIG.8 is a body plan showing, in effect, a series of sections through the hull at stations from B to 5, thus showing the shape of the bow form of the hull 11. Only one side is necessary to show in this way, since the hull 11 is symmetrical both from side to side and fore and aft, so that it represents a view of both sides from either end. The relative positions of the skegs 25, 26 and thrusters l4, 15 are also shown. From this it will be seen that all sections of each station are again made up of a series of straight lines, giving a developable surface, and the relative flatness and width of each station is also evident.

The deck 12 is flat with no camber or pitch, thus eliminating any compound curved shapes and thereby eliminating the costly construction required in normal tugboat building. The rounded square corners 27, 28 and 27', 28 restrict the tugboat from moving under the counters of a ship against which it is pushing. it has fenders as do ordinary tugboats; however, due to the rectangular shape and the rounded-off square corners of the main deck 12, the danger of the tugboat superstructure, the pilot house 13 and deck equipment getting under the flared bows or overhanging stern counters of ships is eliminated, though this problem is commonly experienced with ordinary tugboats.

At each end of the deck 12 are buoyancy compartments 30 and 31, which form part of the forward and after ballast tanks. In this way, reserve buoyancy is obtained, and loss of waterplane is minimized. Even if the deck level 12 should go under water at one end, the vessels longitudinal and transverse stability remain, so that if the tugboat 10 is pitching up and down at the ends, it is still quite stable, due to these special buoyancy compartments 30 and 31.

The deckhouse 13 itself is quite novel. It is located amidships on the vessels center line and has no opening at deck level, but is watertight with respect to the deck 12. Instead, a stairway 32 leads up to a special level of a deckhouse deck 33, well above the level of the deck 12, and where it will almost never be reached by water. There is a watertight door 34 there, which is normally kept closed, and all the quarters for crew and all the remaining parts of the deckhouse 13 inside are kept watertight in this manner. This makes it impossible to capsize the tugboat 10 from forces of its own thrusters 14, or from violent winds or seas. The engines 45 (FIG. 5), which project above the main deck 12 because of the shallow hull 11, are in the hold 38, in the lower part of the hull 11, and are completely protected by the deckhouse 13, which is directly above them, so that the tugboat is virtually unsinkable.

A very novel feature is that the deckhouse 13 is hinged at one end by hinges 35, so that it can be opened by a hydraulic device 36 which both opens it and retains it against falling when it passes over center. It can gently be brought to rest with the top 37 of the deckhouse 13 against one of the buoyancy compartments 30. This opens the entire space 38 beneath the deckhouse 13, enabling easy access through a very large opening 39 to the engines 45 and auxiliary machinery and to all the interior of the tugboat 10.

The pilothouse 13 has excellent visibility, with outwardly sloping windows 40 enabling the operator to have an unrestricted view up and down, as well as horizontally, in all directions and, being the same in all directions, it enables operation in eitherway in either direction. There may be dual controls, but their location is centered that is, near amidships and in the center line.

Another feature of the invention is that at one or both ends there is a pair of adjustable pusher knees 41, 42 which can ordinarily (FIG. 2) be stowed flush within the buoyancy compartments 31 and when in use can be erected to the position shown in FIGS 1 and 3 and 5, where they can push against the stern of a barge as in push towing. When pull towing, a tow rope passes to a towing winch 48 in between these two knees 41, 42, which are at that time flush to enable proper handling and leading of the towline without interference from the large pusher knees 41 and 42. Thus, pulling and pushing can be done with great efficiency from the same end.

Where hawsers or lines are employed in making fast alongside a large vessel for ship handling and docking having high freeboard, so that the lines lead in a vertically upward direction, a double-barreled roller chock 44 is mounted in a novel way at 45 in the bulwark 46 so that, regardless of the angle of the line coming to the tugboat 10, a good lead through the chock 44 to a bollard or capstan 47 can always be obtained.

There may be one thruster at each end of the tugboat 10, or two at one end, as shown in attached drawings. When there is a thruster at each end, each may be situated on the centerline of the tugboat, or the forward one may be slightly off center on one side, while the after one may be either or the centerline or slightly offcenter on the other side. The off-center location prevents turbulent flow of the forward propeller wash from interfering with the effective propulsive function of the after propeller, as it might if it were in line with the forward one when the vessel is going directly ahead or directly astern.

It can be seen that either arrangement of these omnidirectional thrusters l5, 16, together with the flatbottom, double-ended hull 1 1 having shallow draft, can easily effect, by application of thrust, a very rapid response to stopping, turning or swinging the tugboat in a short-radius turn in much less time than an ordinary tugboat.

A Modified Form of Boat for Tending, Lighter- Aboard Ship Systems (FIGS. 9 to 11) the port in order the invention FIGS. 9 This which be smaller. the

Some vessels are designed to carry small barges pre loaded with cargo, in order to reduce theport time of those vessels. Such operations require tenders or tugboats of much greater maneuverability than do conventional operations, inorder to handle efficiently the numerous small barges discharged from and loaded onto such vessels. For such use a tender 50 embodying the principles of theinvention is shown in FIGS.9 to 11. this form of the invention has a hull 51 is very much like the hull 11 except that it is smaller, since the boat 50 itself is to besmaller. The hull 51 is again flat-bottomed, is wide relative to the length, and shallow. The draft-tobeam ratio may, for example, be 1:6.7; beam-to-length ratio is 122.3; and the depth-to-length ratio is 117.8.

The main difference in the hull 51 of this invention is that it has fore-and-aft slots 52 and 53 that extend in from each end and are sealed off to be completely watertight. These slots 52 and 53 are for use with special combined thruster and skeg units 54 and 55. In the example given here, one of these units 54, 55 is adjacent each end of the boat 50 instead of both of them being on one end. Thus, the thruster-skeg unit 54 is forward, and the skeg unit 55 is aft. Each one of these has a thruster portion 56 and a skeg portion 57, and each one of them is mounted upon a stem member 58 which is pivoted at 59 so that it can be raised and lifted through the slot 52 or 53. Also, each unit 54 or 55 is rotatable, so that the thruster 56 can be moved to any position; so again there are omni-directional thrusters.

The boat 50 also has a tall deck tower 60, but in this instance the tower 60 is not pivoted to open and its entrance 61 is at deck level, since this boat 50 has a very simple structure. The tower 60 is again tall, is symmetric, and is centrally located.

The hull 51 also has pusher knees 62, 63 and 64, 65, one pair at each end, and pusher knees 66, 67 along at least one side. Engines 68, 69 through which the thrusters 56 are powered are located on deck adjacent the pivot points 59, and there is no substantial hold in this boat 50, though there is a small space below deck for use with such equipment as is desired to be carried there. A diesel generator can be located directly beneath the central tower or deckhouse 60. This form of the invention is useful for pushing from either end or from the side, the thrusters 56 being turned when the boat 50 is used to push from the side, so that they give power directly toward the direction in which it is going. The thrusters 56 can also be turned 180 when pushing from different ends.

Variations in Number and Position of Thrusters FIGS. (12 and 13) FIGS. 12 and 13 illustrate that thrusters and skegs may be not only of different types but of different number and different construction. Thus inFIGS. 9, 10, the thruster units 54 and 55 are located directly in line with each other fore and aft, while in FIGS. l'through the thrusters l4 and were both aft and parallel to each other. FIG. 12 shows a boat 70 with thruster-skeg units 71 and 72, one located fore and one aft, but out of line with each other so that neither interferes with the other. The thruster 71 is on one side and the other thruster 71 is on the other side of the boat 70. These may be the thruster-skeg units with or without pivoting, or they may be like the units shown in FIGS. 1 through 5.

In FIG. 13 a simple diagram shows a boat 75 of this type with a single power thruster 76 and a single skeg 77, which is just fore of the thruster 76. In this form of the invention, however, the same hull shape applies as it does in all forms of the invention, so that the thruster 76 always lies below the bottom of the hull, and the skeg 77 helps to provide the needed directional stabil ity and alignment.

A Simple Work Boat FIGS. (14 through 16) FIGS. 14 through 16 showa simple work boat 80 embodying the principles of the invention and having a hull 81 like that already described. the proportions and ratios are the same as those for the unit of FIGS. 9 to 11, with the difference being that here there are slots 82 and 83, one for each of two thruster units 84 and 85,

both located aft. These slots 82 and 8;! enable substantially the same action as before. In this particular unit there are also separate skegs 86 and 87, one fore and one aft, in line with the fore-and-aft centerline of the boat 80.

A central tower or deck house 90 is shown, which is of simple construction, is not pivoted and has an entry 91 at the level of a deck 92. A relatively high tower is possible because of the stability of the craft.

Permanent pusher knees 93 and 94 rather than retractable ones are' shown located aft, and there is an A frame 95 at the fore with suitable winches for lifting and translating loads. This simple structure has many of the advantages of the harbor tugboat 10 but at much less expense, and it greatly improves the maneuverability and efficiency in workboat operations not available in thepresently available types of workboats.

To those skilled in the art to which this invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the spirit and scope of the invention. The disclosures and the description herein are purely illustrative and are not intended to be in any sense limiting.

We claim:

1. A tugboat including in combination:

a longitudinally and transversely symmetrical shallow hull having a flat bottom and vertical sides joined to said bottom by a double chine bilge, and symmetrically raked fore-and-aft portions sloping upwardly from said flat bottom, and a generally rectangular outline, as viewed in plan, with flat rectilinear ends and flat rectilinear sides joined by corners that are rounded.

omni-directional thruster means supported by raked portions of said hull and extending down below the level of said bottom, and

. skeg means supported by and below said hull and extending below said thruster means, and centered relative to the fore-and-aft center line of said hull.

2.. The boat of claim 1 having a hull draft-to-beam ratio of about 1:6.

3 The boat of claim 1 having a hull freeboard-to length ratio of about l:l4.

4. The boat of claim I having a completely developable hull surface, said hull being constructed entirely a from flat plates without compound curvature.

5. The boat of claim 1 having a centrally positioned symmetrical square deckhouse surrounded by a deck, said deckhouse being watertight at deck level, said deckhouse having an upper level above said deck having a watertight door at said upper level constituting its only entrance from said deck, and stairs connecting said upper level to said deck.

6. The'boat of claim 5 wherein said deckhouse is hinged at one end to said deck for about 90 of swing to expose a large opening through said deck and a shallow hold below said deck into which said larger opening leads.

7. The boat of claim 6 wherein said tugboat has engines in said shallow hold below said deckhouse, portions thereof lying above the level of said deck in said deckhouse.

8. The boat of claim 5 having a central tower on top of said deckhouse.

9. The boat of claim 5 having at the upper end of said deckhouse a pilot compartment that is four-sided, with windows on each side sloping out from bottom and top.

10. The tugboat of claim 9 having a deck above said pilot compartment.

11. A tugboat including in combination:

a longitudinally and transversely symmetrical shallow hull having a flat bottom and vertical sides joined to said bottom by a double chine bilge and symmetrically raked fore-and-aft portions sloping upwardly from said flat bottom, and a generally rectangular outline, as viewed in plan, with flat rectilinear ends and flat rectilinear sides joined by comers that are rounded, a pair of omni-directional thrusters supported by raked portions of said hull and extending down below the level of said bottom, and

a pair of skegs supported by said hull and extending below said thrusters, at least one said skeg being located adjacent said thrusters and protecting same.

12. A tugboat including in combination:

a longitudinally and transversely symmetrical shallow hull having a flat bottom and a generally rectangular outline, as viewed in plan, with rounded corners, flat ends, and flat sides,

a pair of omni-directional thrusters supported by said hull below the level of said bottom,

a pair of skegs supported by said hull and extending below said thrusters, at least one said skeg being located adjacent said thrusters and protecting same,

a deck on said hull, a flat-topped buoyancy compartment at each end of said deck sealed watertight and extending above deck level, and a pair of pivotally mounted pusher knees adjacent a said buoyancy compartment and swingable into spaces bounded by said buoyancy compartment to a position flush therewith when not in use.

13. The tugboat of claim 1 1 wherein both said thrusters and one said skeg lie adjacent the aft end of said hull, said thrusters being side by side, with that one skeg between them, the other said skeg being locate adjacent the fore end of said hull.

14. A tugboat including in combination:

a longitudinally and transversely symmetrical shallow hull having a flat bottom and a generally rectangular outline, as viewed in plan, with rounded corners, flat ends, and flat sides,

a pair of omni-directional thrusters supported by said hull below the level of said bottom,

a pair of skegs supported by said hull and extending below said thrusters, at least one said skeg being located adjacent said thrusters and protecting same,.and I an upwardly and inwardly inclined bulwark around and above said hull and having a double-barreled roller chock mounted therewith at about 45 to vertical.

15. The tugboat of claim 14 having a flat deck free from sheer, camber, and pitch.

16. A tugboat including in combination:

a longitudinally and transversely symmetrical shallow hull having a flat bottom and vertical sides joined to said bottom by a double chine bilge and symmetrically raked fore-and-aft portions sloping upwardly from said flat bottom and a generally rectangular outline, as viewed in plan, with flat ends and flat sides joined by corners that are rounded,

omni-directional thruster means supported by raked portions of said hull and extending below the level of said bottom, and

skeg means supported by and below said hull and extending below said thruster means, and centered relative to the fore-and-aft center line of said hull,

said hull having a draft-to-beam ratio of about 1:6, a beam-to-water-line-length ratio of about 122.5, a depth-to-length ratio of about 1:9, and a freeboardto-length ratio of about 1:14.

17. The boat of claim 16 having a completely developed hull surface, said hull being constructed entirely from flat plates without compount curvature.

18. The boat of claim 16 having a centrally positioned deck house surrounded by a deck that is flat and free from camber, sheer, and pitch, said deck house being watertight at deck level, and having an upper level above said deck with a watertight door at said upper level, stairs connecting said upper level to said deck, and a central tower above said upper level, having at the upper end a four-sided pilot compartment with windows on each side sloping out from bottom and top, said deckhouse being hinged at one end to said deck for about of swing to expose a large opening through said deck and a hold below said deck into which said larger opening leads.

19. The tugboat of claim 16 having a pair of omnidirectional thrusters constituting said thruster means and a pair of skegs constituting said skeg means, at least one said skeg being located adjacent said thrusters and protecting them.

20. A tugboat including in combination:.

a longitudinally and transversely symmetrical shallow hull having a flat bottom and a generally rectangular outline, as viewed in plan, with rounded corners, flat ends and flat sides;

omni-directional thruster means supported by said hull below the level of said bottom,

skeg means supported by and below said hull and extending below said thruster means, and centered relative to the fore-and-aft center line of said hull,

said hull having a draft-to-beam ratio of about 1:6, a beam-to-water-line-length ratio of about 112.5, a depth-to-length ratio of about 1:9, and a freeboardto-length ratio of about 1:14,

a flat deck on said hull free from sheer, camber and pitch and having at each end a flat-topped buoyancy compartment sealed watertight and extending above deck level, and

a pair of pivotally mounted pusher knees adjacent one said buoyancy compartment and swingable into spaces bounded by said buoyancy compartment to a position flush therewith when not in use.

* l t t UNITED STATES PATENT oFFIcE CERTIFICATE OF CORRECTION Patent No. 3,750,607 Dated August 7, 1973 Inventor(s) David J. Seymour and David Martin It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 46, "combbina-" should read --combina- Column 5, line 38, "1:128" should read -l: l.8-;

line 54, "1.9" should read --l:9--.

Column 8, line 21, "either or" shou'ld'read --either on--;

line 36, after "Systems" insert Figs. 9 to ll-; delete lines 37 and 38 in their entirety; line 40, "theport" should read --the port--; line 43, "inorder" should read --in order-; line 46, "this" should read --This--; line 49, "besmaller" should read --be smaller--; line 51, after the semicolon insert --the--.

Column 9, line 22, delete the parentheses; line 46, delete the parentheses; line 49, "the" should read. --The-.

Column 11, line 43, which is line 1 of claim 15,

. "claim 14" should read --claim ll--.

Column 12, line 11, "compount" should read "compound- Signed and sealed this 12th day of February 1974.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents "QRM PO-l 050 (10-69) USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE I969 o-aes-su, 

1. A tugboat including in combination: a longitudinally and transversely symmetrical shallow hull having a flat bottom and vertical sides joined to said bottom by a double chine bilge, and symmetrically raked fore-and-aft portions sloping upwardly from said flat bottom, and a generally rectangular outline, as viewed in plan, with flat rectilinear ends and flat rectilinear sides joined by corners that are rounded. omni-directional thruster means supported by raked portions of said hull and extending down below the level of said bottom, and skeg means supported by and below said hull and extending below said thruster means, and centered relative to the fore-and-aft center line of said hull.
 2. The boat of claim 1 having a hull draft-to-beam ratio of about 1:6.
 3. The boat of claim 1 having a hull freeboard-to-length ratio of about 1:14.
 4. The boat of claim 1 having a completely developable hull surface, said hull being constructed entirely from flat plates without compound curvature.
 5. The boat of claim 1 having a centrally positioned symmetrical square deckhouse surrounded by a deck, said deckhouse being watertight at deck level, said deckhouse having an upper level above said deck having a watertight door at said upper level constituting its only entrance from said deck, and stairs connecting said upper level to said deck.
 6. The boat of claim 5 wherein said deckhouse is hinged at one end to said deck for about 90* of swing to expose a large opening through said deck and a shallow hold below said deck into which said larger opening leads.
 7. The boat of claim 6 wherein said tugboat has engines in said shallow hold below said deckhouse, portions thereof lying above the level of said deck in said deckhouse.
 8. The boat of claim 5 having a central tower on top of said deckhouse.
 9. The boat of claim 5 having at the upper end of said deckhouse a pilot compartment that is four-sided, with windows on each side sloping out from bottom and top.
 10. The tugboat of claim 9 having a deck above said pilot compartment.
 11. A tugboat including in combination: a longitudinally and transversely symmetrical shallow hull having a flat bottom and vertical sides joined to said bottom by a double chine bilge and symmetrically raked fore-and-aft portions sloping upwardly from said flat bottom, and a generally rectangular outline, as viewed in plan, with flat rectilinear ends and flat rectilinear sides joined by corners that are rounded, a pair of omni-directional thrusters supported by raked portions of said hull and extending down below the level of said bottom, and a pair of skegs supported by said hull and extending below said thrusters, at least one said skeg being located adjacent saiD thrusters and protecting same.
 12. A tugboat including in combination: a longitudinally and transversely symmetrical shallow hull having a flat bottom and a generally rectangular outline, as viewed in plan, with rounded corners, flat ends, and flat sides, a pair of omni-directional thrusters supported by said hull below the level of said bottom, a pair of skegs supported by said hull and extending below said thrusters, at least one said skeg being located adjacent said thrusters and protecting same, a deck on said hull, a flat-topped buoyancy compartment at each end of said deck sealed watertight and extending above deck level, and a pair of pivotally mounted pusher knees adjacent a said buoyancy compartment and swingable into spaces bounded by said buoyancy compartment to a position flush therewith when not in use.
 13. The tugboat of claim 11 wherein both said thrusters and one said skeg lie adjacent the aft end of said hull, said thrusters being side by side, with that one skeg between them, the other said skeg being located adjacent the fore end of said hull.
 14. A tugboat including in combination: a longitudinally and transversely symmetrical shallow hull having a flat bottom and a generally rectangular outline, as viewed in plan, with rounded corners, flat ends, and flat sides, a pair of omni-directional thrusters supported by said hull below the level of said bottom, a pair of skegs supported by said hull and extending below said thrusters, at least one said skeg being located adjacent said thrusters and protecting same, and an upwardly and inwardly inclined bulwark around and above said hull and having a double-barreled roller chock mounted therewith at about 45* to vertical.
 15. The tugboat of claim 14 having a flat deck free from sheer, camber, and pitch.
 16. A tugboat including in combination: a longitudinally and transversely symmetrical shallow hull having a flat bottom and vertical sides joined to said bottom by a double chine bilge and symmetrically raked fore-and-aft portions sloping upwardly from said flat bottom and a generally rectangular outline, as viewed in plan, with flat ends and flat sides joined by corners that are rounded, omni-directional thruster means supported by raked portions of said hull and extending below the level of said bottom, and skeg means supported by and below said hull and extending below said thruster means, and centered relative to the fore-and-aft center line of said hull, said hull having a draft-to-beam ratio of about 1:6, a beam-to-water-line-length ratio of about 1:2.5, a depth-to-length ratio of about 1:9, and a freeboard-to-length ratio of about 1:14.
 17. The boat of claim 16 having a completely developed hull surface, said hull being constructed entirely from flat plates without compount curvature.
 18. The boat of claim 16 having a centrally positioned deck house surrounded by a deck that is flat and free from camber, sheer, and pitch, said deck house being watertight at deck level, and having an upper level above said deck with a watertight door at said upper level, stairs connecting said upper level to said deck, and a central tower above said upper level, having at the upper end a four-sided pilot compartment with windows on each side sloping out from bottom and top, said deckhouse being hinged at one end to said deck for about 90* of swing to expose a large opening through said deck and a hold below said deck into which said larger opening leads.
 19. The tugboat of claim 16 having a pair of omni-directional thrusters constituting said thruster means and a pair of skegs constituting said skeg means, at least one said skeg being located adjacent said thrusters and protecting them.
 20. A tugboat including in combination: a longitudinally and transversely symmetrical shallow hull having a flat bottom and a generally rectangular outline, as viewed in plan, with rounded Corners, flat ends and flat sides; omni-directional thruster means supported by said hull below the level of said bottom, skeg means supported by and below said hull and extending below said thruster means, and centered relative to the fore-and-aft center line of said hull, said hull having a draft-to-beam ratio of about 1:6, a beam-to-water-line-length ratio of about 1:2.5, a depth-to-length ratio of about 1:9, and a freeboard-to-length ratio of about 1:14, a flat deck on said hull free from sheer, camber and pitch and having at each end a flat-topped buoyancy compartment sealed watertight and extending above deck level, and a pair of pivotally mounted pusher knees adjacent one said buoyancy compartment and swingable into spaces bounded by said buoyancy compartment to a position flush therewith when not in use. 